Manufacture of compact combustible explosive charges



mammal), 1948" t 2,434,8TIZ

. Jamea'l'aylor, Saltcoato, and John Whetstone, West-Kilbrlde, Scotland,asa'gnorl to Imperial Great mam Chemical Industries Limited, acorporation of wing." Application 12, 19 44,

No Dra Beral No.

. -'i Claims.

The present invention relates to a new or im:- proved method forthemanufacture of combustibleexplosive charges in compact form,characterised by a .high' gas yield and capable of proa proportionsumcient to obviate the formation 522,106. In Great Britain November ofoxides of nitrogen, and. in the case of charges required for operatingmechanical devices, sufficient to yield a high proportion of permanentduction' in forms of considerable web thickness, 5 cases in the gasesformed. Suitable chromium for the generation of gas pressure, and tocomcompounds are stated to include ammonium, alpact combustible gasproducing explosive charges kall metal. nd rtain other chromates',bichrothereby obtained. mates and polychromates, theammonium and aCompact gas producing charges composed of a P ium ltsin P rticul rly ffeive. combustible explosive material are frequently em- These arereferred to hereinafter as chromate ployed for the actuation of gaspressure operated compounds. According to the aforesaid proposalmechanical devices and gas escape reaction acit is stated that theingredients may be admixed tuated devices, for instance rockets. by amilling operation, and compact compositions Although it is known to usepellets of blackprepared by pressing mixtures containing ampowder, andalthough pellets of compositions 16 monium nitrate and ammoniumbichromate with made from similar ingredients modified by the mineraljelly, bitumen, or paraformaldehyde as presence of inorganic or organicdiluents have the oxidisable'material are exemplified. been suggested ascharges for the production of Notwithstanding the sensitising effect ofthe gas pressure for such purposes, extruded charges chromate compoundsgenerally on the thermal made from smokeless powders consisting essen-20 decomposition of'ammonium nitrate we have now tially of gelatinisednitrocellulose compositions found that compact ammonium'nitrate chargesare now commonly employed on account 01' their containing an oxidisablematerial and sensitised markedly superior gas'yield and otheradvantages. with a chromate compound and suitable for the It is,however, difllcult to produce charges of gela generation of ga p sure ne Produced y a tinised nitrocellulose compositions of any concastingoperation involving at least partial fusion siderable web thickness if avolatile solvent is of the charge provided that there is included inused in their production, since the solvent evapothe compositionsuflicient .of at least one amrates only very slowly from the interiorof the monium nitrate fusion promoting ingredient solid charge, and inpractice it is usually necessary to at ordinary mp tur to r n er the mpoiemploy a composition containing nitroglycerine as tion pourable at atemperature not exceeding apgelatinis'ing agent in order to make andextrude proximat ly 110 to 1 Preferably h hr the composition withoutusing a volatile solvent. mate compound is introduced into the composi-It would, however, be desirable to produce. tion on y after a mixture ta temperature-8t ast compact charges for the generation of gaspresapproximating to pouring temperature has been sure for the aforesaidpurposes without necessifo ed. comprising at least t o um nitating theuse of pressing apparatus and also trate and the fusion promotingingredients. The without consuming the organic nitrates requiredoxidisable material may or may not comprise an for the manufacture ofsmokeless powder. ammoniumznitrate fusion promoting ingredient. It hasbeen proposed in British specification Other constituents can beintroduced before or 453,210 to provide a charge for gas-pressure oper-40 after the chromate compound, but the mainteated devices consistingessentially or largely of nance of compositions containing the chromateammonium nitrate and containing as sensitiser of compound at hightemperature should be avoided its thermal decomposition a chromiumcompound by casting the composition without unnecessary adapted togenerate chromic oxide on heating in delay, otherwise it may showevidence of exother-, the presence of ammonium nitrate, so that the gasmic reaction. evolving composition is capable of undergoing-a Thechromate compound may advantageously self sustained decompositionwithout detonation be an alkali metal or ammonium bichromate or whenignited locally and at ordinary pressure by a polychromate, and theproportion employed may non-detonating igniting element insufflcient ofconveniently amount to from about 2 to 20 per itself to eflect anysubstantial general rise in temcent of the weight of the ammoniumnitrate used. perature of the charge. By ammonium, nitrate fusionpromoting in- According to this previous proposal it is degredients,solidat ordinary temperature, we mean sirable to include in thecomposition a material solid materials (other than chromate compounds)oxidisable by the ammonium nitrate so as to yield adapted when heatedwith ammonium nitrate to gaseous products, this material being presentin temperatures substantially below the fusion point amen ' included inthe composition. The quantity of the fusion promoting ingredientsincluded in the composition, including any water not capable of beingbound as water of crystallisation must be' sufiicient to render themixture pourable at the aforesaid temperature, since above thattemperature the thermal decomposition of the ammonium nitrate by thechromate compound may occur at an appreciable rate, and it will beunderstood that there must be used only such fusion promotingingredients as are capable of being heated with ammonium nitrate andalso with the chromate compound alone without undergoing any substantialdecomposition leading to the formation of gaseous products, at atemperature not exceeding the aforesaid pouring temperature. Olivecolouration indicates chro'mate destruction.

Subject to this proviso there may be used as fusion promotingingredients a wide variety of organic or inorganic substances having theaforesaid properties, whether or not of oxidising or oxidisablecharacter. It is frequently desirable to employ a plurality of fusionpromoting ingredients and these may if desired be of differing chemicalcharacter.

It is often necessary that the amount of oxidisable material in the castcharge should be sufficient not merely to prevent the formation of anyappreciable quantity of oxides of nitrogen, but

also to yield a high proportion of permanent gases, more particularlycarbon monoxide and hydrogen, in the products of its combustion. On theother hand, the formation of an unoxidlsed carbon smoke is seldomdesirable. The employment of ammonium nitrate fusion promotingingredients of oxidisable organic or inorganic character in conjunctionwith ammonium nitrate fusion promoting ingredients of an oxidisingcharacter facilitates the production of cast charges of desirable oxygenbalance at a low pouring temperature.

One useful group of ammonium nitrate fusion promoting ingredientsincludes saline and nonsaline compounds capable of forming eutecticmixtures with ammonium nitrate, whether or not of oxidising character,for instance alkali metal nitrates, alkaline earth metal nitrates,alkali metal chlorides, alkaline earth metal chlorides, magnesiumsulphate and ammonium chloride, or other non-alkaline anhydrous salts.Likewise there may be used various non-saline organic compounds. Auseful group of ammonium nitrate fusion promoters of oxidisablecharacter is provided by weakly basic or non-basic organic aminoderivatives, for instance dicyandi amide, guanidine nitrate,nitroguanidine, acetamide, guanidine and like compounds.

An especially useful category of fusion promoting ingredients is alsoprovided by highly soluble non-alkaline salts containing water ofcrystallisation, whether or not of oxidising character. for instancemagnesium, nitrate hexahydrate, Epsom salts, zinc nitrate hexahydrate,or calcium nitrate tetrahydrate, microcosmic salt and the like. Thewater of crystallisation liberated by such hydrated salts at raisedtemperature has the desirable effect of retarding thermal decompositionof the ammonium bichromate'in the melt. Instead of the hydrated saltscontaining water of crystallisation the anhydrous salts or salts of alower degree by hydration and water in amounts up to that capable ofbeing bound as water of crystallisation when the melt is cooled mayalternatively be employed.

As oxidisable ingredents organic polyhydric compounds are frequently tooeasily oxidised by the polychromates or bichromates to be of serviceaccording to the present invention, but in addition to the fusionpromoting ingredients there may be included in the cast compositionsuspended solid combustibles such as lamp black, graphite, resins or thelike, and the cast composition may also include fusible oxidisableingredients such as nitro-hydrocarbons, hydrocarbons, waxes or the likeemulsified in the melt with the assistance of emulsifying agents such asbentonite or kieselguhr.

The invention is illustrated by the following examples, in which theparts are parts by weight.

Example 1 10 parts magnesium nitrate hexahydrate are fused in a kettlehaving a stirrer and a previously made mixture of 6'? parts powderedammonium,

nitrate, and 15 parts dicyandiamide is then introduced into the kettle,which is heated to to 93 C. and stirred at this temperature until asmuch of the material as possible has fused. 8 parts finely crystallineammonium bichromate are then stirred into the mixture, and the resultingmixture is poured at 90 to 95 C. into wooden moulds of the requiredshape, in which it is allowed to solidify. The resulting cast charge isthereafter removed from the moulds before it has completely cooled.

Example 2 10 parts magnesium nitrate hexahydrate are fused in a heatedkettle fitted with stirring apparatus and a previously prepared mixtureof 56 parts finely crystalline ammonium nitrate, 6 parts potassiumnitrate and 8 parts dicyandiamide is then introduced and heated to C. 2parts bentonite and 11 parts trinitrotoluene are then introduced intothe mixture which is stirred until the molten trinitrotoluene has beenwell emulsifled. 6.5 parts finely crystalline ammonium bichromate arethen stirred into the mixture, which is poured at 95 to 100 G. intowooden moulds of the required form, from which it is removedafterdsolidification, but before it has completely coole Example 3 Amixture of 71 parts finely crystalline ammonium nitrate, 10 partsnitroguanidine, and 7 parts acetamide are melted together with stirringin a kettle at 100 0., 8 parts finely crystalline ammonium bichromateare then introduced into the mixture, whereupon 2 parts bentonite and 2parts carnauba wax introduced, and the mixture is stirred until thecarnauba wax has been well emulsified. The resulting mixture is pouredinto wooden moulds of the required form from which it is removed afterit has solidified, but before it is quite cold.

Example 4 A mixture of 69 parts finely crystalilne ammonium nitrate, 10parts nitroguanidine, 2 parts magnesium nitrate hexahydrate and 7 partsacetamide are mcited'together with stirring in a kettle at 100 C.- 8parts finely crystalline ammonlum bichromate are then introduced intothe it is removed after it has solidified, but before it is quite cold.

Example 56 parts finely crystalline ammonium nitrate, 15.2 partsguanidine nitrate, 11.6 parts nitroguanidine, 2.parts magnesium nitratehexahydrate and 7.2 parts dicyandiamide arefused together at atemperature of 105 0., whereupon 8 parts finely crystalline ammoniumbichromat'e are introduced into the melt with stirring. The melt is thencast into cardboard moulds of the required form, in which it is allowedto solidify, and from which it is removed before the cast has completelycooled.

Example 58 parts finely crystalline ammonium nitrate, 15.2 partsguanidine nitrate, 11.6 parts nitroguanidine and 7.2 parts dicyandiamideare fused together at a temperature'of 105 C. whereupon 8 parts finelycrystalline ammonium bichromate are introduced into the melt, withstirring. The melt is then cast into cardboard moulds of the requiredform, in which it is allowed to solidify. and from which it is removedbefore the cast has completely cooled. Examples 1-6 give orange colouredcasts.

Example 2' 6* yielding a high gas evolution. In using them for thegeneration of pressure it is frequently desirable to employ a relativelysmall quantity of smokeless powder made from nitrocellulose of small webthickness, desirably in conjunction with a small quantity of'blackpowder, to assist their ignition. It is not, however, essential touse smokeless powder. For instance, a cast tubular pellet having anexternal diameter of say 2 inches and an annular thickness of /4 inch,and weighing 2 to 3 lbs. could be ignited by means of an electric powderfuze containing about 15 to 20 grams of blackpowder inserted into thetube.

Having now particularly described and ascertained the nature of our saidinvention, and in what manner the same is to be performed, we declarethat what we claim is:

1. A combustible explosive charge in compact form for the generation ofgas pressure. which comprises ammonium nitrate in preponderatingproportion, in intimate commixture with an oxidizable material, achromate compound adapted to sensitize the thermal decomposition of thecharge, and an ammonium nitrate fusion-promoting ingredient solid atordinary temperatures and adapted to render the charge fluid at atemperature not exceeding 115 0.; said charge being compact andhomogeneous due to solidification of the mixture from fused condition.

2. A process for the production of combustible explosive charges incompact form and suitable form in which it is allowed to solidify andfrom which it is removed before it has completely cooled.

It is sometimes convenient to cast the compositions into Celluloidcontainers which are left in place, and are burned oif in the operationof igniting the charge, instead of casting them into moulds from whichthey are removed. Charges of any desired web thickness in tubular orsolid forms may be made according to the method of the presentinvention. Not only are the novel charges of the invention highlycompact or dense as a result of having solidified from fused condition,but in addition they possess substantial homogeneity or uniformity ofcomposition throughout, in degree characteristic of solidification fromsuch fused condition. The chromate sensitizer is at least in partdissolved in the fluid ammonium nitrate phase at the temperature atwhich the melt is cast, and in any case becomes uniformly-distributedthroughout the melt in extremely intimate and effective asso- The castcharges described in the foregoing examples are all capable of burningwhen ignited,

for the generation of gas pressure which comprises mixing ammoniumnitrate with at least one fusion promoting ingredient solid at ordinarytemperature, said ingredients being adapted to render the chargepourable at a temperature not exceeding about 0., rendering said mixturepourable by at least partial fusion at, a temperature not exceedingabout 115 C., thereafter adding from 2 to 20% based on the weight ofammonium nitrate of a chromate compound adapted to sensitize the thermaldecomposition of the charge, adding at som point during the mixingoperation an oxidizable carbonaceous material sufllcient maximum to binda preponderant proportion of the oxygen present in the combustionproducts of the charge in the form of'carbon monoxide, and casting thecharge by pouring without appreciable delay after addition of thechromate compound.

3. Aprocess for the production of combustible explosive charges incompact form and suitable for the generation of gas pressure whichcomprises mixing ammonium nitrate with at least one oxidizablcarbonaceous fusion promoting ingredient, such ingredients beingsuificient in amount to bind a preponderant proportion of the oxygenpresent in the combustion products of the charge in the form of carbonmonoxide and adapted to render the charge pourable at a temperature notexceeding about 115 rendering said mixture pourable by at least partialfusion at a temperature not exceeding about 115 (3., thereafter addingfrom 2 to 20% based on the weight a v I 7 fusion promoting ingredientconsists oi mazne slum nitrate hexahydrate. I 1

6. A process as defined in claim 2 in which one fusion promotingingredient consists or an alkali metal nitrate.

7. A- process as defined in claim 2 in which the fusion promotingingredients comprise a mixture of (a) an organic amino derivative whichis not more than weakly basic and (b) magnesium nitrate hexahydrate.

JAMES TAYLOR.

Number Name Date 422,514 Emmens Mar. 4, 1890 Number 1,671,792

Number 8 t Name Date Stoops May 29. 1928 Boyd Jan. 12, 1982 Stoops May9, 1988 Spaeth Au. 1, 1938 Naoum July 81, 1934 Holm Apr.17,1937 KirstJan. 31, 1989 Cook Nov. 12, 1940 FOREIGN PATENTS Country Date GreatBritain Feb. 12, 1920 Great Britain Mar. 11, 1936 Great Britain Feb. 15,1938 Great Britain Apr. 20, 1942 Great Britain July 4, 1945

